As semiconductor integrated circuit (IC) devices decrease in size, problems arise as to an increase in electrical resistance of on-chip interconnect wiring lines and an increase in capacitance between wires and between wiring layers. The increases in wire resistivity and in capacitance would result in occurrence of signal transmission delays, which in turn results in a decrease in operating speeds. Thus, remedies for avoiding such problems are under consideration. As one of such remedial measures, an attempt is made to use certain films with low dielectric constants as interlayer dielectric (ILD) insulating films to thereby lower the resistance and capacitance values.
Low dielectric constant films for use as ILD films include a carbon-doped silicon oxide (SiOC) film made of an inorganic material with methyl groups introduced into silicon dioxide (SiO2) and an organic film made of polyallylether derivative or the like, although these materials are in the phase of development. These thin-films are typically 2.6 to 2.9 in dielectric constant. The dielectric constant values remain deficient in view of the quest for highly advanced semiconductor device technologies. Challenges are being made to further reduce the dielectric constant for adaptation to electronic devices of the next generation. One approach to attaining an ultra-low dielectric constant is to introduce holes into an ILD film for reduction of the film density, thereby achieving a film with its dielectric constant ranging from 2.0 to 2.4 in value.
Unfortunately, the advantage of the pore introduction technique does not come without accompanying risks and penalties which follow. When introducing pores into a film, the resulting film decreases in mechanical strength. Such film strength reduction causes a film which is formed on or above a substrate during manufacturing processes to become readily crackable. The film strength reduction also results in a decrease in film properties occurring due to the presence of gas components being absorbed in the pores and/or chemical agents residing therein. This requires execution of additional post-processing for curing any possible deterioration. Due to these penalties, it has been difficult to apply the film having these holes to semiconductor device fabrication processes.
A currently studied alternative approach to achieving the film with its dielectric constant of 2.0 to 2.4 is to lower the dielectric constant of the film-constituting material per se, rather than lowering the dielectric constant by introduction of pores thereinto. One known film that is deemed to satisfy this specification is a fluorinated aromatic-series carbon hydride polymeric film. However, this film is faced with a problem as to occurrence of defects and failures during manufacturing processes. More specifically, the film inherently has fluorine atoms therein and, for the very reason, stays less in adhesion with inorganic films made of silicon dioxide (SiO2), silicon nitride (SiN), silicon carbide (SiC) or else.
As apparent from the foregoing, when using an organic dielectric material film such as the one that is made of fluorinated aromatic-series carbon hydride polymer material, currently available organic dielectric films are less in adhesion at the interface with an inorganic film or a metallic film. This poses a problem that unwanted peel-off or “abruption” defects can readily take place. One known approach to mitigating this problem is disclosed, for example, in Japanese Laid-Open Patent Application No. 2000-183052 (“JP-A-2000-183052”). The technique as taught thereby is to improve the film adhesion by use of a method that has the steps of forming dangling bonds on a substrate surface to be processed and then forming on the surface an organic dielectric material film. The dangling bonds are formed either by performing reverse sputtering of the substrate surface being processed or by forming a layer that contains an increased number of silicon atoms—namely, “Si-rich” layer—in the light of stoichiometry composition.
With this method as taught by JP-A-2000-183052, it is considered that the adhesion is improved while reducing the risk of peel-off occurrence without having to take any particular corrective measures, when compared to the case of mere lamination or “multilayer” of an organic dielectric material film on the substrate being processed. However, this method still fails to provide an intended film with its adhesion large enough to meet the requirements in advanced semiconductor device microfabrication process technologies in recent years. This can be said because the method is incapable of fully removing thermal and physical stresses occurring at an interface between multilayered films. More specifically, the method is designed to directly form dangling bonds on the substrate surface under processing to thereby enhance the adhesion with an organic dielectric material film to be later formed on the surface. The interface is between the inorganic film and the organic dielectric film that is in tight contact with the surface of such inorganic film. In other words, two layers of films are directly adhered together, which are significantly different in characteristics from each other. This characteristics difference causes the interface to suffer from unwanted application of thermal and physical stresses, which leads to the deficiency of interlayer adhesion. Thus a need is felt to provide a technique for enabling achievement of further enhanced adhesivity between organic and inorganic films in highly integrated multilayer semiconductor device structures.